As shown in FIG. 1, a conventional CCD linear sensor has photosensitive regions 21 separated at every pixels. Read-out gate electrodes 22a, 22b and shift registers 23a, 23b are formed common to the photosensitive regions 21. An output unit 25 is formed at the output of the shift registers 23a and 23b.
During a charge accumulating period, signal charges e corresponding to picked-up image information are accumulated in the photosensitive regions 21. During the next reading-out period, a read-out pulse .phi.r is supplied to the read-out gate electrodes 22a and 22b. The signal charges e accumulated in odd-numbered photosensitive regions 21 to be transferred through one read-out gate electrode 22a to one shift register 23a. The signal charges e accumulated in even-numbered photosensitive regions 21 to be transferred through the other read-out gate electrode 22b to the other shift register 23b.
The signal charges e transferred to the shift registers 23a and 23b are further transferred in the horizontal direction, or to an output unit 25 by supplying two transfer pulses .phi.1 and .phi.2 of different phases to the shift registers 23a and 23b. The output unit 25 rearranges sequentially the signal charges e transferred in parallel from the shift registers 23a and 23b into a series of those signal charges e. Then, the output unit 25 converts the signal charges into voltages, which are output as an image signal S from an output terminal .phi.out.
In a conventional CCD linear sensor, however, the signal charges e accumulated in each of the photosensitive region 21 are read-out from a single side of each photosensitive region 21. In other words, the signal charges accumulated in the odd-numbered photosensitive regions 21 are read-out through one read-out gate electrode 22a to one shift register 23a. On the other hand, the signal charges accumulated in the even-numbered photosensitive regions 21 are read-out through the other read-out gate electrode 22b to the other shift register 23b.
Therefore, in the conventional CCD linear sensor, the length L of charge transfer paths of the photosensitive regions 21 which is measured in the reading-out direction is long. So, it takes a long time to read-out the signal charges e. In addition, part of the signal charges e remains within the charge transfer paths, or so-called transfer residue occurs.